The first hurricane of the season grew into a Category 3 storm yesterday after crossing into the warm waters of the Caribbean and is forecast to develop into a monster with 150mph winds before hitting the Yucatan and passing into the Gulf of Mexico, where 4,000 oil and gas platforms are found.

By Wednesday, it could be threatening the US, prompting Texas Governor Rick Perry to suggest people get ready.

In St Lucia, fierce winds tore corrugated metal roofs from dozens of homes and the children's ward of a hospital, whose patients had been evacuated hours earlier. A police spokeswoman, Tamara Charles, said a 62-year-old man was drowned when he tried to retrieve a cow from a rain-swollen river.

In Dominica, a woman and her seven-year-old son were killed when a rain-soaked hillside gave way and crushed the home where they were sleeping.

French authorities on the adjacent island of Martinique said a 90-year-old man died of a heart attack during the storm but it was unclear whether the storm was an aggravating factor. The storm is expected to hit Jamaica tomorrow and climb to Category 4 status.